This invention relates generally to intraocular lenses (IOLs) for implant in the human eye and more specifically to an IOL for implantation in the posterior chamber after an extracapsular cataract extraction (ECE) where the IOL will adhere to the wall of the posterior chamber, i.e. the posterior capsule, by means of an adhesive, either a biological adhesive, or a nonbiological adhesive, and wherein the IOL will prevent the central migration of lens epithelium or other biological contaminents to and within the space between the IOL and the posterior capsule, while simultaneously retaining the lens in its affixed position, and prevent it from migration.
In 1949, the first IOL implants were performed using the Ridley lens. The Ridley lens was held in place by scarring it to the lens capsule and iris. However, it did not remain stable within the eye, as implanted, and further induced corneal dystrophy, glaucoma, and hemorrhaging. It was therefore soon abandoned and replaced by anterior chamber IOLs. The first anterior chamber IOLs were held in place by seating rigid (Strampelli lens, 1953) or by flexible (Danheim lens, 1955) positioning loops in the angle of the anterior chamber. The Strampelli rigid support lens caused corneal dystrophy and had inadequate fixation means which led to epithelial cell loss. The concept, was therefore abandoned. The Danheim lens' fixation loops haptics were made from nylon and were therefore subject to biodegradation in the eye. But, it too was soon abandoned as a concept for this type of implantation.
The problems associated with seating the haptics in the angle of the anterior chamber was addressed by turning to the iris itself for support. The earliest such lens was Epstein's "collar stud" lens which resembled a shirt's stud. It had frequent problems with dislocation due to its extreme weight. Epstein then designed his "Maltese Cross" lens which had four bracing haptics, or loops. Two of the loops were seated behind the iris, while the other two were seated in front of the same.
In 1957, Binkhorst designed his iris clip lens. The original design had four positioning loops--two "L" shaped loops protruded from the back of the lens and were seated behind the iris when inserted, once the other two loops projected from the side of the lens, coplaner with the bottom of the lens, and were seated in front of the iris. Binkhorst further designed a two loop lens and a cloverleaf lens to overcome the problems of dislocation and corneal decompensation associated with the original four loop designs. A number of inventors modified the Brinkhorst lens. For example, Krasnov used sutures to keep the lens fixed, as identified in U.S. Pat. No. 3,986,214. Flom utilized posts which projected rearwardly from the back of the lens, and which penetrated the iris, as shown in U.S. Pat. No. 3,991,426. Furthermore, Barnet utilized magnetic attraction to position the lens by placing magnets at the end of the loops on either side of the iris, as shown in his U.S. Pat. No. 4,298,996. In 1973, Worst designed his medallion lens, which had loops at the approximately three and nine o'clock positions, and a rim around the optical portion and which was sutured to the peripheral structure of the iris.
Early on, lenses had been designed for locating within the posterior chamber. In the mid-1950's Barraquer deigned a lens having incomplete, S-shaped, polypropylene loops which were to be seated in the capsular bag after an ECE. In 1975, Shearing designed a similar lens which also utilized flexibly incomplete loops to position the lens, as shown in his U.S. Pat. No. 4,159,546. Furthermore, the Shearing lens, like the Brinkhorst lens, had many modifications to it, to improve its ability to remain in position, once installed and located. The modifications included the altering of its configuration, size, and number of loops, or through the replacing of the loops with sets of straight pliant hairs, as can be seen in the Hoffer U.S. Pat. No. 4,244,060.
Many of these lenses developed opacified posterior capsules after implantation, and were generally unstable to varying degrees within the eye, once installed, or were damaging to the iris during implantation.
Opacification of the posterior capsule is due to the central migration of lens epithelium which could not be completely removed when the natural lens was removed. The epithelial cells migrate to the space between the implanted IOL and the posterior capsule of the eye. If they proliferate and create new lens fibers then "epithelial pearls" are formed. Some of the cells may metamorphose into myofibroplasts, which gives rise to connective tissue and create what is known as "fibrosis of the posterior capsule." These pearls and/or fibrosis impede and may eventually completely obstruct vision, requiring YAG laser treatment, or discission to restore the clarity. This problem has previously been addressed by Hoffer in his '060 patent, as explained above. Hoffer incorporated, as an integral part of the IOL, an annular lip or ridge which was implaced at the outer periphery of the lens and protruded rearwardly therefrom to the posterior surface of the eye cavity. The ridge, however, was not continuous. It had one or two openings to allow for the insertion of an ophthalmic instrument to perform a discission, a procedure required by IOL opacification due to the presence of such opacification. Because the ridge was not continuous, since the lens does not sit tightly against the posterior capsule and because lens epithelium can migrate, as shown in lab studies, under the ridge, the Hoffer lens is still subject to the formation of pearls and fibrosis after any prolonged usage.
Many posterior chamber lenses use polypropylene, or polymethyl methacrylate, a flexible and memory retaining material, for their positioning hairs or loops ("haptics") that are structured onto the lens, for fixation purposes. After a period of time, though, the memory retaining ability of the haptics may be lost, at which time, the IOLs have a tendency to decenter. Further, implanting lenses with protruding fixation means can damage the Uveal tissue if the haptics are not inserted into the capsular bag. Damage can occur if the haptics are passed through the pupil to be seated in the saddle or cul-de-sac of the posterior chamber. (The ciliary sulcus.) Kelman, in his U.S. Pat. No. 4,534,069, addressed this problem by securing the positioning means in a contracted position around the IOL using a soluble coating. When the lens is inserted through the pupil, the hairs, or loops, then do not damage the iris. Once inside the posterior chamber, the coating dissolves and the positioning means extend to seat themselves in the posterior chamber cul-de-sac. This method, however, requires the surgeon to hold the lens in place while the positioning means extend. Further, this lens is still subject to instability, the gradual formation of the detrimental pearls.
A lens which uses an adhesive such as the body's coagulation system, then such an adhesive could solve the above-mentioned problems. Because the IOL optic would be glued to the posterior capsule, it would remain in place without the fear of haptics eventually failing. And, because the haptics are not required, the potential for Uveal contact would be minimal. Furthermore, the adhesive could form a barrier to the central migration of lens epithelium, and thus prevent post-implantation opacification of the posterior capsule. Presently, there are no such adhesive-lenses available.
The use of a biological glue has, however, been used in other areas of medicine. For example, in 1940, the use of a fibrin coagulum was introduced as a substitute for nerve sutures and was later introduced for use in conjunction with skin grafting. In 1944, the use of aqueous fibrin was examined to replace sutures in the eye wounds. However, human aqueous fibrin was found not to be sufficiently adhesive due to the small amounts of fibrinogen present in the aqueous.
The search for a biological glue for use in the eye slowed until the 1970's. In 1975, a mixture of autogonous platelets, human fibrinogen, and bovine thrombine (pft) were introduced for use in autotransplanted lamellar keratoplasties in rabbits. In this study, the cornea was removed, and the p-f-t mixture was applied in sequence to the lamellar bed. The cornea was then replaced without the use of sutures. A week after surgery, the adhesive began to disappear and fibroplaste growth was evident along the boundary of the adhesive. After two weeks, the adhesive had been absorbed and was no longer visible. The p-f-t adhesive was found to be non-toxic, soft, rubbery and pliable, and to be absorbed by the rabbit. This method, however, also allowed continued epithilial growth. This growth cannot be tolerated when implanting IOLs, for reasons as previously explained, since it will and does lead to opacification of the posterior capsule.
In 1986, an autogenous fibrin sealant consisting of bovine thrombin, plasma, and CaCl.sub.2 was injected into a retinal hole and under the retina to seal retinal detachments in rabbits. This exercise was, however, unsuccessful, in that the results of sealant treated and control retinas were very similar.
In 1987, human fibrinogen concentrate was successfully used to close lens capsule wounds and through-and-through lens perforations. Equal amounts of fibrinogen concentrate and thrombin-CaCl.sub.2 solution were successively applied. The fibrinogen was forced through the perforation path and the thrombin-CaCl.sub.2 was then injected into the posterior and anterior chambers.
Also, as disclosed in the East German patent specification, DD234365Al, the concept of implanting a lens, in conjunction with an adhesive, was shown in 1985. In that particular instance, the artificial eye lens having small holes located spacedly through its periphery was applied by means of a nontoxic nonabsorbable tissue adhesive, by applying the adhesive through the holes, to implant the lens to the posterior capsule of the eye. While this particular concept was to provide a means for adhesively connecting an artificial lens to the posterior capsule, it is undetected from the published specification as to whether the adhesive formed a perfect seal, entirely around the periphery of the implanted lens, and as to whether or not posterior capsule opacification would thereby be alleviated, after its implantation. Since only four such holes were shown in the patent's specification, and the adhesive was applied only at four discrete locations, it is likely that complete sealing could not, or would not, have taken place.
In addition to the foregoing, various biological glues have been developed by a company named Bio-Polymers, Inc., and which adhesive or coating formulation comprises a bioadhesive polyphenolic protein component, with a proteinaceous substance, including cross linking agents, to promote the desired properties of the formulation during usage. The formulations are identified for usage as adhesives, amongst other uses, for orthopedic repair to bones, etc., as an ophthalmic adhesive for aiding the healing of perforations, lacerations or incisions, as an ophthalmic adhesive for attaching the retina and for repair of lenses, and the like. Other biological adhesives of this Company are for use in promoting cell adhesion in tissue culture systems, may be used in cell-coated prostheses, or for use for implantable materials.
Furthermore, there are other settable adhesives that have been available in the art, generally of the non-biological type, and which also have even included in their usage medical applications, such as for application to wounds, cuts, or the like, to stimulate sealing or closure of such abrasions.